Implementation method of state machine and coroutine scheduler of Golang function

In Golang, a function can be regarded as a state machine, which will enter different states according to different input parameters. Golang's coroutine scheduler realizes scheduling and interaction between coroutines by controlling the state machine of coroutine functions. Below we will introduce the implementation methods of the state machine and coroutine scheduler of Golang functions respectively.

State machine of Golang function

In Golang, a function can be regarded as a state machine, because the function can enter different states according to different input parameters. For example, the following function:

func greeting(name string, timeOfDay string) {
    if timeOfDay == "morning" {
        fmt.Println("Good morning, " + name)
    } else if timeOfDay == "afternoon" {
        fmt.Println("Good afternoon, " + name)
    } else if timeOfDay == "evening" {
        fmt.Println("Good evening, " + name)
    } else {
        fmt.Println("Invalid time of day specified")
    }
}

This function will output different greetings based on the input parameter timeOfDay. This function is a simple state machine because it can enter different states according to different input parameters.

In fact, Golang's coroutine implements state machines in a similar way. Within the coroutine, you can monitor multiple channels through the select statement and implement different state transfers based on the status of the channel. For example, the following coroutine:

func processRequests(requests chan string, responses chan string) {
    for {
        select {
        case request := <-requests:
            // Process request and send response
            response := processRequest(request)
            responses <- response
        default:
            // No requests, so sleep for a short time
            time.Sleep(10 * time.Millisecond)
        }
    }
}

This coroutine will listen to the requests channel and the responses channel. If there is a request from the requests channel, it will enter the processing state, and after the processing is completed, the result will be sent to the responses channel. If there are no requests, it will sleep for a while.

Golang’s coroutine scheduler implementation method

Golang’s coroutine scheduler can be regarded as a special coroutine that monitors the status of all coroutines and schedules them as needed. Golang's coroutine scheduler mainly has two implementation methods: preemptive scheduling and cooperative scheduling.

Preemptive scheduling means that after a coroutine is assigned a time slice, it will be forcibly executed within a certain period of time until the time slice is used up. This scheduling method does not rely on the behavior of the coroutine itself, so it can effectively prevent a certain coroutine from occupying CPU resources for a long time. Golang's coroutine scheduler uses preemptive scheduling.

Collaborative scheduling means that a coroutine will only switch to other coroutines when it actively gives up its execution rights. This scheduling method relies on the behavior of the coroutine itself, so it is necessary to ensure that the coroutine does not occupy CPU resources for a long time in order to achieve good scheduling effects.

For Golang's coroutine scheduler, the specific implementation adopts the M:N scheduling method, that is, M coroutines are mapped to N system threads for execution. This method can not only make full use of the performance of multi-core CPUs, but also effectively prevent competition and state interference between different coroutines. Inside the scheduler, a priority-based time-round scheduling algorithm is used to ensure that high-priority coroutines can be scheduled in time and ensure the real-time and stability of the system.

To sum up, functions and coroutines in Golang can be regarded as state machines, and the coroutine scheduler is a special coroutine that implements preemptive scheduling and M:N scheduling. These characteristics make Golang outstanding in high-concurrency and high-reliability application scenarios, making it the language of choice for many Internet companies and engineers.

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